The invention relates to a chemical mechanical polishing (CMP) process which is used for flattening an insulated layer embedded in a trench and an interlayer dielectric in a multi-layer wiring process, in particular relates to a dresser which makes it possible to dress and condition a polishing pad surface deteriorated by polishing treatment, and a method for dressing a polishing pad by using this dresser.
Hitherto, the CMP process used for a semiconductor apparatus has been used for flattening a thin layer, for example, an insulated layer or a metal layer formed on a semiconductor wafer by CVD or the like.
The CMP process is a process for making a thin layer on the surface of a semiconductor wafer flat by infiltrating a polishing material containing polishing particles, which is referred to as a slurry, into a polishing pad set up on a polishing plate and rotating the polishing pad accompanied with rotation of the polishing plate to polish the semiconductor wafer with the rotating polishing pad. Polishing many wafers by this process, i.e., carrying out polishing treatment of wafers many times, results in a problem that the surface of the polishing pad becomes rough to be deteriorated. Hitherto, surface-treatment, referred to as dressing, has been conducted, in order to restore the rough surface to the initial condition thereof as much as possible.
In the CMP process which is used for manufacturing a semiconductor apparatus, polishing is carried out under a condition that a polishing material is present between the polishing pad and the semiconductor wafer. A material for the polishing pad used for polishing includes various materials. A material which is commonly used is a polyurethane foam. The polishing pad composed of the polyurethane foam has in the surface thereof a large number of fines bores, and keeps a polishing material in the bores to enable polishing. However, if the polishing treatment of a semiconductor wafer is conducted many times in application of the CMP process to manufacture a semiconductor apparatus, reaction products and particles of the polishing material are gradually pressed against the inner portions of the bores so that they are confined into the bores. Polishing under such a condition causes a polishing rate and uniformity from polishing to be decreased.
When the urethane foam is used for the polishing pad, an initial treatment is necessary which is for making the surface of the polishing pad rough to some extent at the start of use of the pad and which is called conditioning. Making the surface rough by this treatment is indispensable for obtaining a stable polishing rate and uniformity from polishing.
It is known that the polishing pad is remarkably deteriorated by adding, into the polishing material, a material having a high viscosity such as a high molecular surfactant or a polysaccharide besides polishing particles. Attention has been paid to a serious problem that use of such a deteriorated polishing pad causes drop in a yield rate in the CMP process for a semiconductor device wafer in which fine patterns are formed at a high density.
Hitherto, treatment for setting a pad, which is referred to dressing, has been conducted to remove off an alien substance with which the bores are blocked and scrape off a rough surface of the pad. For the dressing, there is usually used a diamond dresser in which diamond particles are incorporated into a resin or on which diamond particles are electrodeposited. The diamond dresser makes it possible to remove off the alien substance substantially completely because of scraping off the surface layer of the polyurethane foam; however, it causes the surface state of the polishing pad to be returned to the surface state before being subjected to the initial treatment. Therefore, unless after the dressing treatment the pad is conditioned to make the surface thereof rough, it is impossible to reproduce a stable polishing rate and uniformity form polishing. A silicon wafer may be used for the conditioning. Specifically, the polishing pad may be conditioned by polishing the silicon wafer with the polishing pad for about 60 minutes, i.e., the dummy-polishing treatment with the silicon wafer. Much time is spent on the dummy-polishing treatment with the silicon wafer. Consequently, hitherto a decline in productivity in this process has been a serious problem.
The present invention has been accomplished on the basis of such a situation. The object of the present invention is to provide a method for dressing a polishing pad, a polishing apparatus, and a method for manufacturing a semiconductor apparatus which make it possible to prevent productivity-drop resulted from conditioning treatment of a polishing pad deteriorated by polishing the surface of a semiconductor wafer in the CMP process.
The object of the present invention is to provide a method for dressing a polishing pad, a polishing apparatus, and a method for manufacturing a semiconductor apparatus which make it possible to reduce dust with dishing being controlled, make the life of the polishing pad longer and stabilize a polishing rate.
The first feature of a method for dressing a polishing pad according to the present invention comprise the steps of: polishing at least one semiconductor wafer, in which a polishing material containing polishing particles is applied to a polishing surface of the semiconductor wafer while the semiconductor wafer is polished with the polishing pad; and dressing the surface of the polishing pad deteriorated by polishing the semiconductor wafer, with a ceramic dresser. The second feature of a method for dressing a polishing pad according to the present invention comprises the steps: dressing a used surface of the polishing pad with a diamond dresser; dressing with a ceramic dresser the surface of the polishing pad treated with the diamond dresser; polishing at least one semiconductor wafer, in which a polishing material containing polishing particles is applied to a polishing surface of the semiconductor wafer while the semiconductor wafer is polished with the polishing pad; and dressing the surface of the polishing pad deteriorated by polishing at least one semiconductor wafer, with the ceramic dresser.
The invention may further comprise the step of dressing the polishing pad again with the ceramic dresser, after the deteriorated polishing pad restored by using the ceramic dresser is deteriorated by polishing the semiconductor wafer. The polishing pad may be dressed with the diamond dresser, after conducting the above-mentioned dressing step with the ceramic dresser plural times. The polishing pad dressed with the diamond dresser may be dressed with the ceramic dresser for restoration, before the polishing pad is used for a further polishing treatment. The surface of the ceramic dresser may have at least one step.
The polishing apparatus according to the present invention comprises: a polishing pad for polishing a semiconductor wafer; a means for supplying a polishing material to the polishing pad; a polishing plate driven by a driving shaft, in which the polishing pad is disposed on the surface of the polishing plate; and a ceramic dresser disposed so as to be pressed against the polishing pad. A diamond dresser may be further fitted up. The apparatus may have a controlling unit for controlling the rotating number of the ceramic dresser and the press pressure of the ceramic dresser against the polishing pad.
The method for manufacturing a semiconductor apparatus according to the invention comprises step: arranging a polishing pad on a polishing plate of a polishing apparatus; giving plural semiconductor wafers the treatment of applying a polishing material containing polishing particles to respective polishing surfaces of the semiconductor wafers while polishing respective films to be polished on the respective polishing surfaces, with the polishing pad; and dressing with a ceramic dresser the surface of the polishing pad deteriorated by polishing the respective films to be polished of the plural semiconductor wafers. The polishing pad may be rotated by rotation of the polishing plate, and the semiconductor wafers may be polished while they are pressed against the rotating polishing pad. The respective semiconductor wafers may be removed off from the polishing pad, and subsequently the ceramic dresser may be pressed against the rotating polishing pad to dress the polishing pad. The ceramic dresser may be pressed against the polishing pad when the respective semiconductor wafers are pressed against the polishing pad, thereby carrying out the dressing treatment accompanied with the polishing treatment.
The ceramic dresser and the diamond dresser may be pressed against the polishing pad when the respective semiconductor wafers are pressed against the polishing pad, thereby carrying out the dressing treatment with the ceramic dresser and the dressing treatment with the diamond dresser accompanied with the polishing treatment. Pure water may be supplied to the polishing pad when the respective films to be polished are polished. An additive for controlling dishing may be supplied to the polishing pad when the respective films to be polished are polished. The additive for controlling dishing may comprise a hydrophilic polysaccharide.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinbefore.